1. Field of the Invention
The present invention relates generally to the field of apparatus and methods for changing motor oil in internal combustion engines. More specifically, the invention relates to a computer-controlled system for removing used oil from a vehicle engine, supplying the engine with fresh oil, and purging the system of residual oil, all in an environmentally protective manner.
2. Description of Related Art
Metal parts that make contact with one another within internal combustion engines are lubricated by lubricants, generally called "motor oils" which must be replaced at regular intervals to optimize engine performance and to prevent damage or malfunction from abrasive or corrosive contaminants in the lubricant. Traditionally, the task of replacing used motor oil with fresh motor oil has involved: 1) manually removing a crankcase oilpan plug from beneath an engine; 2) gravity draining the used oil into a receptacle exposed to the ambient environment; and 3) refilling the crankcase by gravity through an oil filling port, either from a number of small containers, or from a fresh oil bulk dispensing tank or barrel.
This operation is often messy, time consuming, and environmentally unsound, exposing the used oil to the environment. Furthermore, changing oil in this manner often leaves a substantial residual quantity of used oil in the crankcase, since the gravity draining is inefficient, especially if the used crankcase oil has become excessively thickened due to overlong use. Still further, both the filling and draining operations often expose service station personnel to contact with the oil, an occurrence that is perceived to pose some health risks, especially in connection with used oil.
Various attempts have been made in the prior art to render the foregoing task less messy, less time-consuming, less environmentally hazardous and generally safer and more convenient. Most of these attempts have employed some form of suction device to extract the used oil, and some have also provided for a pressurized injection of fresh oil. The various prior art oil changing systems, however, suffer from one or more drawbacks, such as inadequate or nonexistent automation, non-portability, poor internal system status checks, minimal environmental safeguards, or the inability to directly monitor and/or control the quantity of oil extracted or supplied.
For example, U.S. Pat. No. 3,216,527--Lewis discloses an engine crankcase oil changing system that employs suction for oil extraction, and pressurized air for supplying fresh oil through the dipstick tube of the engine. This system requires the permanent installation of some parts on the engine itself, and it employs separate devices for vacuum generation and for pressurizing the fresh oil flow. There is no measurement of the quantity of spent oil extracted, nor are status checks provided during any of the operations.
U.S. Pat. No. 3,810,487--Cable et al. discloses a truck mounted mobile oil changing system that employs air pressure to inject fresh oil into an engine's crankcase. While the system is capable of supplying a plurality of engine fluids from multiple sources, both mounted on the truck and remote from it, there is no significant degree of automation. Spent oil is drained from the vehicle by gravity flow into a waste oil receptacle, exposing the spent oil to the environment.
U.S. Pat. No. 5,372,219--Peralta discloses a reversible pump driven system for extracting and adding motor oil to an engine, employing a single multiway valve for directing fluid flow. The system is mounted within the engine compartment of the vehicle, and thus can be used only for the engine in that vehicle. There is no provision for measuring fluid flow, and thus no part of the extraction or refilling process is automated on the basis of the volume of the oil delivered or removed. Nor are there any built-in means for automatically checking fluid levels in supply tanks or waste tanks, or for testing for vacuum presence or low voltage level, during operation of the system.
There has thus been a long-felt, but as yet unfilled need for an engine oil changing system that employs a single pump to both extract used oil and to inject fresh oil, and that automatically and directly measures fluid flow both into and out of the engine in real time to control both the filling and extraction functions. There is a further need for such an oil changing system that can be made either mobile or stationary, and that performs the entire oil exchange operation without exposure of the oil to the environment, and without exposing the operator to the used oil. There is a still further need for such an oil changing system that incorporates computer controlled operational and status checks and automated error messages to assure the efficient and successful completion of the oil exchange operation.